Abstract

The Gibbs' energies of formation of BaCuO2, Y2Cu2O5 and Y2BaCuO5 from component oxides have been measured using solid state galvanic cells incorporating CaF2 as the solid electrolyte under pure oxygen at a pressure of 1.01×105 Pa 〈BaO〉 + 〈CuO〉 → 〈BaCuO2〉 ΔGf,oxo(± 0.3) (kJ mol−1)=−63.4−0.0525T(K) 〈Y2O3〉 + 2〈CuO〉 → 〈Y2Cu2O2〉 ΔGf,oxo(± 0.3) (kJ mol−1)=18.47−0.0219T(K) 〈Y2O3〉 + 〈BaO〉 + 〈CuO〉 → 〈Y2BaCuO5〉 ΔGf,oxo(± 0.7) (kJ mol−1)=−72.5−0.0793T(K) Because the superconducting compound YBa2Cu3O7−δ coexists with any two of the phases CuO, BaCuO2 and Y2BaCuO5, the data on BaCuO2 and Y2BaCuO5 obtained in this study provide the basis for the evaluation of the Gibbs' energy of formation of the 1-2-3 compound at high temperatures.